1. Field of the Invention
This invention relates to the field of a fluid operated rotary actuator having a particular seal arrangement.
2. DESCRIPTION OF THE PRIOR ART
Rotary actuator type devices which operate with an oscillatory motion require an unusual seal between the rotating and stationary members. The purpose of this slidable seal is to minimize leakage and improve operational efficiency of the device. Typical examples of seal configuration as shown in U.S. Pat No. 3,446,120 to Sneen. This patent shows seals between both the shaft and body of the actuator and between the mechanical stop and the body. Other examples are shown in the U.S. Pat. No. 3,426,654 to Laughman which combines an O-ring and a glide ring or cap ring of nylon or teflon to complete the sliding seal. Single piece seals are shown in U.S. Pat. No. 2,902,009 in a rotating actuator are well known and used in the art. However, only the Sneen patent shows a dual lip seal in a rotary actuator for sealing the high pressure inlet chamber from the low back pressure that is developed in such devices. There are two basic problems with the seals that have been discussed; first, the shape of the area which the seal is sealing is a rectangular section. This is especially difficult to seal at the corners or intersections of the side walls and arcuate surfaces. Second, the seals must be expandable and rub the mating surface in order to provide a seal and hence must, by necessity, be replaced when they become worn. As wear is occurring, the leadkage rate will increase because the geometry of the surfaces is not absolute and the seals have only a limited ability to move or expand to compensate for such imperfection since they are usually held in a groove or a plate affixed to the rotationg member. Seen's patent tries to reduce this effect by having a second seal in his design.
My invention overcomes these short-comings by allowing the moving seal to float so that geometric imperfections in the construction can be overcome by the ability of the seal assembly to move and fill any voids which occur in the rotation of the shaft. It is an object of this invention to provide a floating seal between the arcuate surface of a rotary actuator and the rotating element.
It is an object of this invention to provide a floating seal between the rotating element and the stationary stop in a rotary actuator.
It is an object of this invention to provide replaceable bumper stops on both the rotating member and stationary stop in a rotary actuator.
It is an object of this invention to provide a bronze or bearing type material for the seal carrier.
It is an object of this invention to provide seals in a rotary actuator so they can operate from either a liquid or a gas source.